spell check stopped working on Mac book air

Is it not working in many applications, or is this specific to Pages?

If specific to Pages, I've seen this occur when pasting from Microsoft Word. To clear the issue:

Deleting the System Preference or other .plist file

com.apple.iWork.Pages.plist

The plist file will get recreated upon application use, if Pages look for the Pages plist file, or the affected application.